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第6章 计算机的运算方法（上） 测试

1、单选题：
‌计算机中的数据可以存放在___中。‍
选项：
A: 寄存器
B: 主存
C: 硬盘
D: 都可以
答案: 【 都可以】点我阅读全文

Scanning

1、单选题：
​Read the passage "The Discovery of X-rays" quickly and choose the paragraph(s) which contain(s) the answer(s). You may choose more than one answer for question 3. ‌​‌The Discovery of X-rays‌​ ‌Par. 1 Except for a brief description of the Compton effect, and a few other remarks, we have postponed the discussion of X-rays until the present chapter because it is particularly convenient to treat X-ray spectra after treating optical spectra. Although this ordering may have given the reader a distorted impression of the historical importance of X-rays, this impression will be corrected shortly as we describe the crucial role played by X-rays in the development of modern physics.‌Par. 2 X-rays were discovered in 1895 by Roentgen while studying the phenomena of gaseous discharge. Using a cathode ray tube with a high voltage of several tens of kilovolts, he noticed that salts of barium would fluoresce when brought near the tube, although nothing visible was emitted by the tube. This effect persisted when the tube was wrapped with a layer of black cardboard. Roentgen soon established that the agency responsible for the fluorescence originated at the point at which the stream of energetic electrons struck the glass wall of the tube. Because of its unknown nature, he gave this agency the name X-rays. He found that X-rays could manifest themselves by darkening wrapped photographic plates, discharging charged electroscopes, as well as by causing fluorescence in a number of different substances. He also found that X-rays can penetrate considerable thicknesses of materials of low atomic number, whereas substances of high atomic number are relatively opaque. Roentgen took the first steps in identifying the nature of X-rays by using a system of slits to show that (1) they travel in straight lines, and that (2) they are uncharged, because they are not deflected by electric or magnetic fields.‌Par. 3 The discovery of X-rays aroused the interest of all physicists, and many joined in the investigation of their properties. In 1899 Haga and Wind performed a single slit diffraction experiment with X-rays which showed that (3) X-rays are a wave motion phenomenon, and, from the size of the diffraction pattern, their wavelength could be estimated to be 10-8 cm. In 1906 Barkla proved that (4) the waves are transverse by showing that they can be polarized by scattering from many materials.‌Par. 4 There is, of course, no longer anything unknown about the nature of X-rays. They are electromagnetic radiation of exactly the same nature as visible light, except that their wavelength is several orders of magnitude shorter. This conclusion follows from comparing properties 1 through 4 with the similar properties of visible light, but it was actually postulated by Thomson several years before all these properties were known. Thomson argued that X-rays are electromagnetic radiation because such radiation would be expected to be emitted from the point at which the electrons strike the wall of a cathode ray tube. At this point, the electrons suffer very violent accelerations in coming to a stop and, according to classical electromagnetic theory, all accelerated charged particles emit electromagnetic radiations. We shall see later that this explanation of the production of X-rays is at least partially correct.‌Par. 5 In common with other electromagnetic radiations, X-rays exhibit particle-like aspects as well as wave-like aspects. The reader will recall that the Compton effect, which is one of the most convincing demonstrations of the existence of quanta, was originally observed with electromagnetic radiation in the X-ray region of wavelengths.‌​‌​When were X-rays discovered?‌
选项：
A: Par. 1
B: Par. 2
C: Par. 3
D: Par. 4
E: Par. 5
答案: 【 Par. 2】点我阅读全文

第一章 单元测试题

1、单选题：
‍供应大脑半球前3/5部血液的血管是‏
选项：
A: 椎-基底动脉系统
B: 颈内动脉系统
C: 前交通动脉
D: 大脑中动脉
答案: 【 颈内动脉系统】点我阅读全文

三相异步电动机控制线路

1、单选题：
‏三相异步电动机连续运行控制电路中起自锁作用的触点是（      ）​‏​‏​
选项：
A: 交流接触器主触点
B: 交流接触器动断辅助触点
C: 交流接触器动合辅助触点
D: 交流接触器线圈
答案: 【 交流接触器动合辅助触点】点我阅读全文

1.2随堂检测

1、单选题：
‏砌体工程用的块材不包括‍
选项：
A: 烧结普通砖
B: 煤渣砖
C: 陶粒混凝土砌块
D: 玻璃砖
答案: 【 玻璃砖】点我阅读全文

单元测试一

1、单选题：
​web标准的制定者是（      ）。‌
选项：
A: 微软
B: 万维网联盟（W3C）
C: 网景公司（Netscape）
D: IBM公司
答案: 【 万维网联盟（W3C）】点我阅读全文

选择与判断题

1、单选题：
‏曲中“去似朝云无觅处”一句在演唱时，两处的自由延长号的演唱处理应该是（         ）‌
选项：
A: 随意延长
B: 不用延长
C: 此处为乐曲终止处
D: 根据对作品情绪的理解做适当延长
答案: 【 根据对作品情绪的理解做适当延长】点我阅读全文

第二章 测试

1、单选题：

‍一物体在1秒内沿半径R=1m的圆周上从A点运动到B点，如图所示，则物体的平均速度是：

‏

‍

‏选项：
A: 大小为2m/s，方向由A指向B；
B: 大小为2m/s，方向由B指向A；
C: 大小为3.14m/s，方向为A点切线方向；
D: 大小为3.14m/s，方向为B点切线方向。
答案: 【 大小为2m/s，方向由A指向B；】点我阅读全文

第1-3讲单元测验

1、单选题：
计量运动主要是由美国地理学家发起的，并形成了（  ）个学派？‎‎
选项：
A: 1个学派
B: 2个学派
C: 3个学派
D: 4个学派
答案: 【 3个学派】点我阅读全文

逻辑代数基础

1、单选题：
‍同模拟信号相比，数字信号具有________性。一个数字信号只有________种取值，分别表示为________和________。‎
选项：
A: 连续性，2，1，2
B: 数字性，2，1，2
C: 对偶性，2，0，1
D: 离散性，2，0，1
答案: 【 离散性，2，0，1】点我阅读全文